The mine expects you to sneak through undead enemies that can walk faster than you can sneak, so it's a luck challenge. Especially since you can't know where the temple door is (or that there is a temple in the mines...) and the logs you find tell you everything, except the most vital information!
Avoiding the knights in the mines is REALLY easy once you know how. You don't even have to sneak for a single second.
1) Let a char with invisibility scout the area and discover the second portal.
2) Leave the mines through the entrance.
3) Teleport your whole party to the second portal.
4) Avoid the last two knights which is really easy if you follow the southern (trapped) path to the temple door.
